Electrophoresis is a well known principle used in separating a mixture of components of differing molecular weight, and/or size, such as proteins, and has had particular applicability in the medical field in separating the components of blood serum for testing and in large-scale production of special protein products. The process also has wide applicability in the industrial separation and recovery of other mixed components.
In the electrophoresis process the mixture to be separated is applied to one end of a neutral supporting medium, such as paper, gel (acrylamide, starch or agar), or any of the other known supporting media. An electrical potential difference is induced between the end surfaces of the medium by a power source and transferred to the medium through an electrolyte or buffer solution. The different components in the mixture adopt electrical charges and have different constants of mobility in the medium in accordance with their charges, sizes or molecular weights and pH of the medium, and thus move at different rates in the medium under the influence of the electric field, thereby effectively becoming separated in space in the medium.
One of the major recognized disadvantages of the prior devices is their inability to continually automatically collect the different components of the mixture as they are separated by the supporting medium. The general method of operation is to apply a batch of the mixture to be separated to the supporting medium, wait for the components to separate, and then sequentially collect the components in different containers as they reach the bottom of the medium.
One attempt at increasing the speed of collecting the separated components (but still not automatically) uses a series of individual supporting media to simultaneously separate a series of applications of a mixture, or of different mixtures, as disclosed in U.S. Pat. No. 3,576,727 to B. L. Evott. While this increases the amount of mixture separated, it still maintains the same main disadvantage of the single-sample operation in requiring constant supervision for sequentially collecting the components at proper moments after they separate.
Other devices, such as the Brinkmann Preparative Electrophoresis System, which is commercially available, do provide apparatus for continuously separating the components of a mixture. Such a system, however, cannot use a supporting medium, as required in the most desirable systems, so as to obtain maximum accuracy and purity of separation. In the Brinkmann device, a buffer solution is fed in a continuous stream between a pair of closely spaced planar parallel plates, with an electrical field parallel to the plates and at right angles to the stream direction. As the mixture travels with the buffer flow, the components with different electrophoretic mobilities are driven by the electric field at different angles from the flow path and are collected at respective given points at the end of the planar plate opposite from that which the mixture was introduced. The apparatus is expensive, complicated, extremely bulky, requires sophisticated controls, and has limited separation capacity. Further, it requires bulk flow of electrolyte and components with high lateral rate of movement to be mixed at the lateral limiting membranes.